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package javax.sql;

import java.sql.Connection;
import java.sql.SQLException;

/**
 * An object that provides hooks for connection pool management.
 * A <code>PooledConnection</code> object
 * represents a physical connection to a data source.  The connection
 * can be recycled rather than being closed when an application is
 * finished with it, thus reducing the number of connections that
 * need to be made.
 * <p>
 * An application programmer does not use the <code>PooledConnection</code>
 * interface directly; rather, it is used by a middle tier infrastructure
 * that manages the pooling of connections.
 * <p>
 * When an application calls the method <code>DataSource.getConnection</code>,
 * it gets back a <code>Connection</code> object.  If connection pooling is
 * being done, that <code>Connection</code> object is actually a handle to
 * a <code>PooledConnection</code> object, which is a physical connection.
 * <p>
 * The connection pool manager, typically the application server, maintains
 * a pool of <code>PooledConnection</code> objects.  If there is a
 * <code>PooledConnection</code> object available in the pool, the
 * connection pool manager returns a <code>Connection</code> object that
 * is a handle to that physical connection.
 * If no <code>PooledConnection</code> object is available, the
 * connection pool manager calls the <code>ConnectionPoolDataSource</code>
 * method <code>getPoolConnection</code> to create a new physical connection.  The
 * JDBC driver implementing <code>ConnectionPoolDataSource</code> creates a
 * new <code>PooledConnection</code> object and returns a handle to it.
 * <p>
 * When an application closes a connection, it calls the <code>Connection</code>
 * method <code>close</code>. When connection pooling is being done,
 * the connection pool manager is notified because it has registered itself as
 * a <code>ConnectionEventListener</code> object using the
 * <code>ConnectionPool</code> method <code>addConnectionEventListener</code>.
 * The connection pool manager deactivates the handle to
 * the <code>PooledConnection</code> object and  returns the
 * <code>PooledConnection</code> object to the pool of connections so that
 * it can be used again.  Thus, when an application closes its connection,
 * the underlying physical connection is recycled rather than being closed.
 * <p>
 * The physical connection is not closed until the connection pool manager
 * calls the <code>PooledConnection</code> method <code>close</code>.
 * This method is generally called to have an orderly shutdown of the server or
 * if a fatal error has made the connection unusable.
 *
 * <p>
 * A connection pool manager is often also a statement pool manager, maintaining
 * a pool of <code>PreparedStatement</code> objects.
 * When an application closes a prepared statement, it calls the
 * <code>PreparedStatement</code>
 * method <code>close</code>. When <code>Statement</code> pooling is being done,
 * the pool manager is notified because it has registered itself as
 * a <code>StatementEventListener</code> object using the
 * <code>ConnectionPool</code> method <code>addStatementEventListener</code>.
 * Thus, when an application closes its  <code>PreparedStatement</code>,
 * the underlying prepared statement is recycled rather than being closed.
 * <p>
 *
 * @since 1.4
 */

public interface PooledConnection {

    /**
     * Creates and returns a <code>Connection</code> object that is a handle
     * for the physical connection that
     * this <code>PooledConnection</code> object represents.
     * The connection pool manager calls this method when an application has
     * called the method <code>DataSource.getConnection</code> and there are
     * no <code>PooledConnection</code> objects available. See the
     * {@link PooledConnection interface description} for more information.
     *
     * @return a <code>Connection</code> object that is a handle to
     * this <code>PooledConnection</code> object
     * @throws SQLException                             if a database access error occurs
     * @throws java.sql.SQLFeatureNotSupportedException if the JDBC driver does not support
     *                                                  this method
     * @since 1.4
     */
    Connection getConnection() throws SQLException;

    /**
     * Closes the physical connection that this <code>PooledConnection</code>
     * object represents.  An application never calls this method directly;
     * it is called by the connection pool module, or manager.
     * <p>
     * See the {@link PooledConnection interface description} for more
     * information.
     *
     * @throws SQLException                             if a database access error occurs
     * @throws java.sql.SQLFeatureNotSupportedException if the JDBC driver does not support
     *                                                  this method
     * @since 1.4
     */
    void close() throws SQLException;

    /**
     * Registers the given event listener so that it will be notified
     * when an event occurs on this <code>PooledConnection</code> object.
     *
     * @param listener a component, usually the connection pool manager,
     *                 that has implemented the
     *                 <code>ConnectionEventListener</code> interface and wants to be
     *                 notified when the connection is closed or has an error
     * @see #removeConnectionEventListener
     */
    void addConnectionEventListener(ConnectionEventListener listener);

    /**
     * Removes the given event listener from the list of components that
     * will be notified when an event occurs on this
     * <code>PooledConnection</code> object.
     *
     * @param listener a component, usually the connection pool manager,
     *                 that has implemented the
     *                 <code>ConnectionEventListener</code> interface and
     *                 been registered with this <code>PooledConnection</code> object as
     *                 a listener
     * @see #addConnectionEventListener
     */
    void removeConnectionEventListener(ConnectionEventListener listener);

    /**
     * Registers a <code>StatementEventListener</code> with this <code>PooledConnection</code> object.  Components that
     * wish to be notified when  <code>PreparedStatement</code>s created by the
     * connection are closed or are detected to be invalid may use this method
     * to register a <code>StatementEventListener</code> with this <code>PooledConnection</code> object.
     * <p>
     *
     * @param listener an component which implements the <code>StatementEventListener</code>
     *                 interface that is to be registered with this <code>PooledConnection</code> object
     *                 <p>
     * @since 1.6
     */
    public void addStatementEventListener(StatementEventListener listener);

    /**
     * Removes the specified <code>StatementEventListener</code> from the list of
     * components that will be notified when the driver detects that a
     * <code>PreparedStatement</code> has been closed or is invalid.
     * <p>
     *
     * @param listener the component which implements the
     *                 <code>StatementEventListener</code> interface that was previously
     *                 registered with this <code>PooledConnection</code> object
     *                 <p>
     * @since 1.6
     */
    public void removeStatementEventListener(StatementEventListener listener);

}
